The transition between low Eb and Db (or vice versa), is troublesome for many flutists. If you can't do it smoothly, it doesn't mean that you are incompetent, it simply means that you need to practice doing it until it gets smoother. Also, you can try a little trick that many players use. Rub the tip of your RH pinky along the side of your nose where it joins your cheek. Most people have an excess of skin oil at that spot and rubbing it with your pinky will transfer some skin oil to the finger. That will make it slide more smoothly between the keys. As absurd as that may sound, try it. I think you will find that it helps.

I find playing in the key of Db awkward. ....mostly because I don't play in that key often. Then...to hover around those low notes back and forth, over and over....not pleasant.

My sound is much better and fingers much faster on my daughter's student flute for the low Db??? My open hole flute, b foot and small fingers seem to make this a challenge. However, the higher places sound drastically better on my flute so I can't use hers.

My head screw can easily spin around if twisted now that it is colder outside so maybe I have a headcork issue too interfering with a rich, full low sound???

A great portion of the awkwardness one experiences in the extreme lower register is mostly because the ring and pinkie fingers are controlled by the same tendon. The other fingers have independent tendons that control them.